The focus of this conference will be on the problems posed by quantitative cancer risk assessment with particular emphasis on the use of biologically-based models for species to species and low dose extrapolation. The goal of the conference is to bring together experts in several disciplines -- risk assessment, carcinogenesis modelling, pharmacokinetics, molecular epidemiology -- in order to highlight and clarify important scientific issues in quantitative cancer risk assessment. Emphasis will be on the application of quantitative (mathematical, statistical, etc.) methodologies to the scientific issues to be discussed. Chairing this 1989 Conference will be Dr. Suresh H. Moolgavkar of the Fred Hutchinson Cancer Research Center and the University of Washington (Seattle). Serving as Conference Director will be Dr. Donald L. Thomsen, Jr. (SIMS).